Alvocidib prodrugs having increased bioavailability

ABSTRACT

Compounds having the following structure (I): 
     
       
         
         
             
             
         
       
     
     or a stereoisomer, tautomer or pharmaceutically acceptable salt thereof, wherein one of R 1 , R 2  or R 3  is —P(═O)(OH) 2 , and the other two of R 1 , R 2  and R 3  are each H, are provided. Pharmaceutical compositions comprising the compounds, and methods for use of the compounds for treating diseases associated with overexpression of a cyclin-dependent kinase (CDK) are also provided.

BACKGROUND Technical Field

The present invention is generally directed to phosphate prodrugs of alvocidib and use of the same for treatment of cancer.

Description of the Related Art

Cyclin-dependent kinases (CDKs) are important regulators that control the timing and coordination of the cell cycle. CDKs form reversible complexes with their obligate cyclin partners to control transition through key junctures in the cell cycle. For example, the activated CDK4-cyclin D1 complex controls progression through the G1 phase of the cell cycle, while the CDK1-cyclin B1 complex controls entry into the mitotic phase of the cell cycle. Endogenous cyclin dependent kinase inhibitory proteins (CDKIs) are known to bind either the CDK or cyclin component and inhibit the kinase activity of the complex. In many tumors such as melanomas, pancreatic and esophageal cancers, these natural CDKIs are either absent or mutated. Thus, selective CDK inhibitors may prove to be effective chemotherapeutic agents.

Alvocidib (also known as Flavopiridol) is a synthetic flavone having the following structure:

Alvocidib is a potent and selective inhibitor of the CDKs and has antitumor activity against various tumor cells lines, such as human lung carcinoma and breast carcinoma and also inhibits tumor growth in xenograft models. Alvocidib has been shown to induce arrest in both the G1 and G2 phases of the cell cycle and also inhibit polymerase II driven transcription by inhibiting CDK9. By inhibiting CDK9, which forms part of the complex known as the positive transcription elongation factor or P-TEFb, alvocidib treatment reduces the expression of key oncogenes such MYC and key anti-apoptotic proteins such as MCL1. Accordingly, alvocidib is an attractive therapeutic agent for cancer and is currently undergoing clinical trials in relapsed/refractory AML patients.

Oral administration of alvocidib has been limited by gastrointestinal toxicity and limited oral bioavailability. Further, preclinical studies suggest that prolonged exposure may be important for maximizing alvocidib's activity. Accordingly, continuous intravenous infusion schedules have been extensively explored in human trials. Alternative hybrid dosing, including an intravenous bolus dose followed by a slow infusion have also been explored, but to date there have been no reports of orally delivering a therapeutically effective amount of alvocidib.

While progress has been made, there remains a need in the art for increasing the oral bioavailability of alvocidib. The present invention fulfills this need and provides related advantages.

BRIEF SUMMARY

In brief, embodiments of the present invention provide phosphate prodrugs of alvocidib having increased bioavailability relative to the alvocidib parent compound. Accordingly, in one embodiment is provided a compound having the following structure (I):

or a stereoisomer, tautomer or pharmaceutically acceptable salt thereof, wherein:

one of R¹, R² or R³ is —P(═O)(OH)₂, and the other two of R¹, R² and R³ are each H.

Other embodiments are directed to a pharmaceutical composition comprising a pharmaceutically acceptable carrier or excipient and a compound of structure (I). Methods for use of the compound of structure (I), and pharmaceutical compositions comprising the same, for treatment of a disease associated with overexpression of a cyclin-dependent kinase (CDK) in a mammal in need thereof are also provided.

These and other aspects of the invention will be apparent upon reference to the following detailed description. To this end, various references are set forth herein which describe in more detail certain background information, procedures, compounds and/or compositions, and are each hereby incorporated by reference in their entirety.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the pharmacokinetic profile of alvocidib and compound IB following the administration of compound IB to Sprague Dawley rats.

FIG. 2A-D depict the body weights of mice treated with a single dose (FIG. 2A-B orally, FIG. 2C-D intravenously) of alvocidib or compound IB.

FIG. 3A-D show the body weights of mice treated with daily doses (FIG. 3A-B orally, FIG. 3C-D intravenously) of alvocidib or compound IB.

FIG. 4A-B show body weights and food consumption of rats treated with a single dose (orally) of alvocidib or compound IB.

FIG. 5A-B show in vivo tumor volume and body weight after dosing with compound IB during a xenograft efficacy study.

FIG. 6A-B depict reduction of MCL-1 protein expression following treatment with compound IB during a xenograft pharmacodynamic study.

DETAILED DESCRIPTION

In the following description, certain specific details are set forth in order to provide a thorough understanding of various embodiments of the invention. However, one skilled in the art will understand that the invention may be practiced without these details.

Unless the context requires otherwise, throughout the present specification and claims, the word “comprise” and variations thereof, such as, “comprises” and “comprising” are to be construed in an open, inclusive sense, that is, as “including, but not limited to”.

Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, the appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features or characteristics may be combined in any suitable manner in one or more embodiments.

Embodiments of the present invention include phosphate prodrugs of alvocidib. “Phosphate” refers to the —OP(═O)(OH)₂ moiety. For ease of illustration the phosphate moieties herein are often depicted in the di-protonated form, but also exist in the mono-protonated (—OP(═O)(OH)(O⁻)) and unprotonated forms (—OP(═O)(O⁻)₂), depending on pH. The mono- and unprotonated forms will typically be associated with a counterion, such that the compounds are in the form of a pharmaceutically acceptable salt. Such mono- and unprotonated forms, and their pharmaceutically acceptable salts, are encompassed within the scope of the inventions, even if not specifically illustrated in the chemical structures.

“Prodrug” is meant to indicate a compound that may be converted under physiological conditions or by solvolysis to a biologically active compound described herein (e.g., compound of structure (I)). Thus, the term “prodrug” refers to a precursor of a biologically active compound that is pharmaceutically acceptable. In some aspects, a prodrug is inactive when administered to a subject, but is converted in vivo to an active compound, for example, by hydrolysis. The prodrug compound often offers advantages of solubility, tissue compatibility or delayed release in a mammalian organism (see, e.g., Bundgard, H., Design of Prodrugs (1985), pp. 7-9, 21-24 (Elsevier, Amsterdam). A discussion of prodrugs is provided in Higuchi, T., et al., “Pro-drugs as Novel Delivery Systems,” A.C.S. Symposium Series, Vol. 14, and in Bioreversible Carriers in Drug Design, ed. Edward B. Roche, American Pharmaceutical Association and Pergamon Press, 1987, both of which are incorporated in full by reference herein.

A “compound of the invention” refers to a compound of structure (I), and its substructures, as defined herein.

Embodiments of the invention disclosed herein are also meant to encompass all pharmaceutically acceptable compounds of structure (I) being isotopically-labelled by having one or more atoms replaced by an atom having a different atomic mass or mass number. Examples of isotopes that can be incorporated into the disclosed compounds include isotopes of hydrogen, carbon, nitrogen, oxygen, phosphorous, fluorine, chlorine, and iodine, such as ²H, ³H, ¹¹C, ¹³C, ¹⁴C, ¹³N, ¹⁵N, ¹⁵O, ¹⁷O, ¹⁸O, ³¹P, ³²P, ³⁵S, ¹⁸F, ³⁶Cl, ¹²³I, and ¹²⁵I, respectively. These radiolabelled compounds could be useful to help determine or measure the effectiveness of the compounds, by characterizing, for example, the site or mode of action, or binding affinity to pharmacologically important site of action. Certain isotopically-labelled compounds of structure (I), for example, those incorporating a radioactive isotope, are useful in drug and/or substrate tissue distribution studies. The radioactive isotopes tritium, i.e. ³H, and carbon-14, i.e. ¹⁴C, are particularly useful for this purpose in view of their ease of incorporation and ready means of detection.

Substitution with heavier isotopes such as deuterium, i.e. ²H, may afford certain therapeutic advantages resulting from greater metabolic stability, for example, increased in vivo half-life or reduced dosage requirements, and hence may be preferred in some circumstances.

Substitution with positron emitting isotopes, such as ¹¹C, ¹⁸F, ¹⁵O and ¹³N, can be useful in Positron Emission Topography (PET) studies for examining substrate receptor occupancy. Isotopically-labeled compounds of structure (I) can generally be prepared by conventional techniques known to those skilled in the art or by processes analogous to those described in the Preparations and Examples as set out below using an appropriate isotopically-labeled reagent in place of the non-labeled reagent previously employed.

Embodiments of the invention disclosed herein are also meant to encompass the in vivo metabolic products of the disclosed compounds. Such products may result from, for example, the oxidation, reduction, hydrolysis, amidation, esterification, and the like of the administered compound, primarily due to enzymatic processes. Accordingly, embodiments of the invention include compounds produced by a process comprising administering a compound of this invention to a mammal for a period of time sufficient to yield a metabolic product thereof. Such products are typically identified by administering a radiolabelled compound of the invention in a detectable dose to an animal, such as rat, mouse, guinea pig, monkey, or to human, allowing sufficient time for metabolism to occur, and isolating its conversion products from the urine, blood or other biological samples.

“Pharmaceutically acceptable carrier, diluent or excipient” includes without limitation any adjuvant, carrier, excipient, glidant, sweetening agent, diluent, preservative, dye/colorant, flavor enhancer, surfactant, wetting agent, dispersing agent, suspending agent, stabilizer, isotonic agent, solvent, or emulsifier which has been approved by the United States Food and Drug Administration as being acceptable for use in humans or domestic animals.

“Pharmaceutically acceptable salt” includes both acid and base addition salts.

“Pharmaceutically acceptable acid addition salt” refers to those salts which retain the biological effectiveness and properties of the free bases, which are not biologically or otherwise undesirable, and which are formed with inorganic acids such as, but are not limited to, hydrochloric acid, hydrobromic acid, sulfuric acid, nitric acid, phosphoric acid and the like, and organic acids such as, but not limited to, acetic acid, 2,2-dichloroacetic acid, adipic acid, alginic acid, ascorbic acid, aspartic acid, benzenesulfonic acid, benzoic acid, 4-acetamidobenzoic acid, camphoric acid, camphor-10-sulfonic acid, capric acid, caproic acid, caprylic acid, carbonic acid, cinnamic acid, citric acid, cyclamic acid, dodecylsulfuric acid, ethane-1,2-disulfonic acid, ethanesulfonic acid, 2-hydroxyethanesulfonic acid, formic acid, fumaric acid, galactaric acid, gentisic acid, glucoheptonic acid, gluconic acid, glucuronic acid, glutamic acid, glutaric acid, 2-oxo-glutaric acid, glycerophosphoric acid, glycolic acid, hippuric acid, isobutyric acid, lactic acid, lactobionic acid, lauric acid, maleic acid, malic acid, malonic acid, mandelic acid, methanesulfonic acid, mucic acid, naphthalene-1,5-disulfonic acid, naphthalene-2-sulfonic acid, 1-hydroxy-2-naphthoic acid, nicotinic acid, oleic acid, orotic acid, oxalic acid, palmitic acid, pamoic acid, propionic acid, pyroglutamic acid, pyruvic acid, salicylic acid, 4-aminosalicylic acid, sebacic acid, stearic acid, succinic acid, tartaric acid, thiocyanic acid, p-toluenesulfonic acid, trifluoroacetic acid, undecylenic acid, and the like.

“Pharmaceutically acceptable base addition salt” refers to those salts which retain the biological effectiveness and properties of the free acids, which are not biologically or otherwise undesirable. These salts are prepared from addition of an inorganic base or an organic base to the free acid. Salts derived from inorganic bases include, but are not limited to, the sodium, potassium, lithium, ammonium, calcium, magnesium, iron, zinc, copper, manganese, aluminum salts and the like. Preferred inorganic salts are the ammonium, sodium, potassium, calcium, and magnesium salts. Salts derived from organic bases include, but are not limited to, salts of primary, secondary, and tertiary amines, substituted amines including naturally occurring substituted amines, cyclic amines and basic ion exchange resins, such as ammonia, isopropylamine, trimethylamine, diethylamine, triethylamine, tripropylamine, diethanolamine, ethanolamine, deanol, 2-dimethylaminoethanol, 2-diethylaminoethanol, dicyclohexylamine, lysine, arginine, histidine, caffeine, procaine, hydrabamine, choline, betaine, benethamine, benzathine, ethylenediamine, glucosamine, methylglucamine, theobromine, triethanolamine, tromethamine, purines, piperazine, piperidine, N-ethylpiperidine, polyamine resins and the like. Particularly preferred organic bases are isopropylamine, diethylamine, ethanolamine, trimethylamine, dicyclohexylamine, choline and caffeine.

Often crystallizations produce a solvate of the compound of the invention. As used herein, the term “solvate” refers to an aggregate that comprises one or more molecules of a compound of the invention with one or more molecules of solvent. The solvent may be water, in which case the solvate may be a hydrate. Alternatively, the solvent may be an organic solvent. Thus, embodiments of the compounds of the present invention may exist as a hydrate, including a monohydrate, dihydrate, hemihydrate, sesquihydrate, trihydrate, tetrahydrate and the like, as well as the corresponding solvated forms. Embodiments of the compound of the invention may be true solvates, while in other cases, the compound of the invention may merely retain adventitious water or be a mixture of water plus some adventitious solvent.

A “pharmaceutical composition” refers to a formulation of a compound of the invention and a medium generally accepted in the art for the delivery of the biologically active compound to mammals, e.g., humans. Such a medium includes all pharmaceutically acceptable carriers, diluents or excipients therefor.

“Mammal” includes humans and both domestic animals such as laboratory animals and household pets (e.g., cats, dogs, swine, cattle, sheep, goats, horses, rabbits), and non-domestic animals such as wildlife and the like.

“Effective amount” or “therapeutically effective amount” refers to that amount of a compound of the invention which, when administered to a mammal, preferably a human, is sufficient to effect treatment, as defined below, of a disease associated with overexpression of a cyclin-dependent kinase (CDK) in the mammal, preferably a human. The amount of a compound of the invention which constitutes a “therapeutically effective amount” will vary depending on the compound, the condition and its severity, the manner of administration, and the age of the mammal to be treated, but can be determined routinely by one of ordinary skill in the art having regard to his own knowledge and to this disclosure.

“Treating” or “treatment” as used herein covers the treatment of the disease or condition of interest in a mammal, preferably a human, having the disease or condition of interest, and includes:

-   -   (i) preventing the disease or condition from occurring in a         mammal, in particular, when such mammal is predisposed to the         condition but has not yet been diagnosed as having it;     -   (ii) inhibiting the disease or condition, i.e., arresting its         development;     -   (iii) relieving the disease or condition, i.e., causing         regression of the disease or condition; or     -   (iv) relieving the symptoms resulting from the disease or         condition, i.e., relieving pain without addressing the         underlying disease or condition. As used herein, the terms         “disease” and “condition” may be used interchangeably or may be         different in that the particular malady or condition may not         have a known causative agent (so that etiology has not yet been         worked out) and it is therefore not yet recognized as a disease         but only as an undesirable condition or syndrome, wherein a more         or less specific set of symptoms have been identified by         clinicians.

The compounds of the invention, or their pharmaceutically acceptable salts may contain one or more asymmetric centers and may thus give rise to enantiomers, diastereomers, and other stereoisomeric forms that may be defined, in terms of absolute stereochemistry, as (R)- or (S)- or, as (D)- or (L)- for amino acids. The present invention is meant to include all such possible isomers, as well as their racemic and optically pure forms. Optically active (+) and (−), (R)- and (S)-, or (D)- and (L)- isomers may be prepared using chiral synthons or chiral reagents, or resolved using conventional techniques, for example, chromatography and fractional crystallization. Conventional techniques for the preparation/isolation of individual enantiomers include chiral synthesis from a suitable optically pure precursor or resolution of the racemate (or the racemate of a salt or derivative) using, for example, chiral high pressure liquid chromatography (HPLC). When the compounds described herein contain olefinic double bonds or other centers of geometric asymmetry, and unless specified otherwise, it is intended that the compounds include both E and Z geometric isomers. Likewise, all tautomeric forms are also intended to be included.

A “stereoisomer” refers to a compound made up of the same atoms bonded by the same bonds but having different three-dimensional structures, which are not interchangeable. Embodiments of the present invention contemplate various stereoisomers and mixtures thereof and includes “enantiomers”, which refers to two stereoisomers whose molecules are nonsuperimposeable mirror images of one another.

A “tautomer” refers to a proton shift from one atom of a molecule to another atom of the same molecule. Embodiments of the present invention include tautomers of any said compounds.

I. Compounds

As noted above, embodiments of the present disclosure are directed to prodrugs of alvocidib having increased bioavailability relative to the parent compound. Surprisingly, experiments performed in support of the present invention demonstrate that a monophosphate analogue of alvocidib has a bioavailability of approximately 1.3 times the parent alvocidib compound when delivered orally to CD-1 mice and more than 8 times that of the related diphosphate prodrugs. The presently disclosed monophosphate compounds are metabolized to alvocidib in vivo and, while not wishing to be bound by theory, it is believed that the increase in bioavailability of alvocidib released from the monophosphate prodrug compared to the alvocidib parent compound is related to a slower rate of metabolism of the prodrug compared to alvocidib. Other expected advantages of the present compounds include increased solubility in typical pharmaceutical formulations, in water and in bodily fluids, and decreased toxicity relative to the alvocidib parent compound when administered orally.

Accordingly, in one embodiment a compound is provided having the following structure (I):

or a stereoisomer, tautomer or pharmaceutically acceptable salt thereof, wherein:

one of R¹, R² or R³ is —P(═O)(OH)₂, and the other two of R¹, R² and R³ are each H.

In certain embodiments, the compound has the following structure (I′):

In some other embodiments, the compound has the following structure (IA):

In some more embodiments, the compound has the following structure (IA′):

In yet other embodiments, the compound has the following structure (IB):

In other different embodiments, the compound has the following structure (IB′):

In still more embodiments, the compound has the following structure (IC):

In some other different embodiments, the compound has the following structure (IC′):

In some embodiments, any of the foregoing compounds are in the form of a pharmaceutically acceptable salt. The salt may be an acid addition salt or a base addition salt. For example, the salt may be an amine salt formed by protonation of the N-methyl piperazine moiety (e.g., HCl salt and the like). In other embodiments, the salt is formed at the phosphate, and the compounds are in the form of mono- or di-salts of the phosphate group (e.g., mono- or disodium phosphate salt and the like). All pharmaceutically acceptable salts of the foregoing compounds are included in the scope of the invention.

Also provided are pharmaceutical compositions comprising a pharmaceutically acceptable carrier or excipient and any of the foregoing compounds (i.e., a compound of structure (I), (I′), (IA), (IA′), (IB), (IB′), (IC) or (IC′)). Advantageously, the presently disclosed compounds have increased bioavailability relative to the alvocidib parent compound, and thus certain embodiments are directed to the foregoing pharmaceutical compositions formulated for oral delivery. Any of the carriers and/or excipients known in the art for oral formulation may be used in these embodiments, in addition to other carriers and/or excipients derivable by one of ordinary skill in the art.

For the purposes of administration, the compounds of the present invention may be administered as a raw chemical or may be formulated as pharmaceutical compositions. Embodiments of the pharmaceutical compositions of the present invention comprise a compound of structure (I) and a pharmaceutically acceptable carrier, diluent or excipient. The compound of structure (I) is present in the composition in an amount which is effective to treat a particular disease or condition of interest—that is, typically in an amount sufficient to treat a disease associated with overexpression of a cyclin-dependent kinase (CDK), and preferably with acceptable toxicity to the patient. Bioavailability of compounds of structure (I) can be determined by one skilled in the art, for example, as described in the Examples below. Appropriate concentrations and dosages can be readily determined by one skilled in the art.

Administration of the compounds of the invention, or their pharmaceutically acceptable salts, in pure form or in an appropriate pharmaceutical composition, can be carried out via any of the accepted modes of administration of agents for serving similar utilities. The pharmaceutical compositions of embodiments of the invention can be prepared by combining a compound of the invention with an appropriate pharmaceutically acceptable carrier, diluent or excipient, and may be formulated into preparations in solid, semi-solid, liquid or gaseous forms, such as tablets, capsules, powders, granules, ointments, solutions, suppositories, injections, inhalants, gels, microspheres, and aerosols. Typical routes of administering such pharmaceutical compositions include, without limitation, oral, topical, transdermal, inhalation, parenteral, sublingual, buccal, rectal, vaginal, and intranasal. The term parenteral as used herein includes subcutaneous injections, intravenous, intramuscular, intrasternal injection or infusion techniques. Pharmaceutical compositions of the invention are formulated so as to allow the active ingredients contained therein to be bioavailable upon administration of the composition to a patient. Compositions that will be administered to a subject or patient take the form of one or more dosage units, where for example, a tablet may be a single dosage unit, and a container of a compound of the invention in aerosol form may hold a plurality of dosage units. Actual methods of preparing such dosage forms are known, or will be apparent, to those skilled in this art; for example, see Remington: The Science and Practice of Pharmacy, 20th Edition (Philadelphia College of Pharmacy and Science, 2000). The composition to be administered will, in any event, contain a therapeutically effective amount of a compound of the invention, or a pharmaceutically acceptable salt thereof, for treatment of a disease or condition of interest in accordance with the teachings of this invention.

A pharmaceutical composition of some embodiments of the invention may be in the form of a solid or liquid. In one aspect, the carrier(s) are particulate, so that the compositions are, for example, in tablet or powder form. The carrier(s) may be liquid, with the compositions being, for example, an oral syrup, injectable liquid or an aerosol, which is useful in, for example, inhalatory administration.

When intended for oral administration, the pharmaceutical composition is preferably in either solid or liquid form, where semi-solid, semi-liquid, suspension and gel forms are included within the forms considered herein as either solid or liquid.

As a solid composition for oral administration, the pharmaceutical composition may be formulated into a powder, granule, compressed tablet, pill, capsule, chewing gum, wafer or the like form. Such a solid composition will typically contain one or more inert diluents or edible carriers. In addition, one or more of the following may be present: binders such as carboxymethylcellulose, ethyl cellulose, microcrystalline cellulose, gum tragacanth or gelatin; excipients such as starch, lactose or dextrins, disintegrating agents such as alginic acid, sodium alginate, Primogel, corn starch and the like; lubricants such as magnesium stearate or Sterotex; glidants such as colloidal silicon dioxide; sweetening agents such as sucrose or saccharin; a flavoring agent such as peppermint, methyl salicylate or orange flavoring; and a coloring agent.

When the pharmaceutical composition is in the form of a capsule, for example, a gelatin capsule, it may contain, in addition to materials of the above type, a liquid carrier such as polyethylene glycol or oil.

The pharmaceutical composition may be in the form of a liquid, for example, an elixir, syrup, solution, emulsion or suspension. The liquid may be for oral administration or for delivery by injection, as two examples. When intended for oral administration, preferred composition contain, in addition to the present compounds, one or more of a sweetening agent, preservatives, dye/colorant and flavor enhancer. In a composition intended to be administered by injection, one or more of a surfactant, preservative, wetting agent, dispersing agent, suspending agent, buffer, stabilizer and isotonic agent may be included.

The liquid pharmaceutical compositions of some embodiments of the invention, whether they be solutions, suspensions or other like form, may include one or more of the following adjuvants: sterile diluents such as water for injection, saline solution, preferably physiological saline, Ringer's solution, isotonic sodium chloride, fixed oils such as synthetic mono or diglycerides which may serve as the solvent or suspending medium, polyethylene glycols, glycerin, propylene glycol or other solvents; antibacterial agents such as benzyl alcohol or methyl paraben; antioxidants such as ascorbic acid or sodium bisulfite; chelating agents such as ethylenediaminetetraacetic acid; buffers such as acetates, citrates or phosphates and agents for the adjustment of tonicity such as sodium chloride or dextrose. The parenteral preparation can be enclosed in ampoules, disposable syringes or multiple dose vials made of glass or plastic. Physiological saline is a preferred adjuvant. An injectable pharmaceutical composition is preferably sterile.

A liquid pharmaceutical composition of certain embodiments of the invention intended for either parenteral or oral administration should contain an amount of a compound of the invention such that a suitable dosage will be obtained.

In some embodiments, the pharmaceutical composition of the invention may be intended for topical administration, in which case the carrier may suitably comprise a solution, emulsion, ointment or gel base. The base, for example, may comprise one or more of the following: petrolatum, lanolin, polyethylene glycols, bee wax, mineral oil, diluents such as water and alcohol, and emulsifiers and stabilizers. Thickening agents may be present in a pharmaceutical composition for topical administration. If intended for transdermal administration, the composition may include a transdermal patch or iontophoresis device.

The pharmaceutical composition of various embodiments of the invention may be intended for rectal administration, in the form, for example, of a suppository, which will melt in the rectum and release the drug. The composition for rectal administration may contain an oleaginous base as a suitable nonirritating excipient. Such bases include, without limitation, lanolin, cocoa butter and polyethylene glycol.

Embodiments of the pharmaceutical composition of the invention may include various materials, which modify the physical form of a solid or liquid dosage unit. For example, the composition may include materials that form a coating shell around the active ingredients. The materials that form the coating shell are typically inert, and may be selected from, for example, sugar, shellac, and other enteric coating agents. Alternatively, the active ingredients may be encased in a gelatin capsule.

The pharmaceutical composition of some embodiments of the invention in solid or liquid form may include an agent that binds to the compound of the invention and thereby assists in the delivery of the compound. Suitable agents that may act in this capacity include a monoclonal or polyclonal antibody, a protein or a liposome.

The pharmaceutical composition of other embodiments of the invention may consist of dosage units that can be administered as an aerosol. The term aerosol is used to denote a variety of systems ranging from those of colloidal nature to systems consisting of pressurized packages. Delivery may be by a liquefied or compressed gas or by a suitable pump system that dispenses the active ingredients. Aerosols of compounds of the invention may be delivered in single phase, bi-phasic, or tri-phasic systems in order to deliver the active ingredient(s). Delivery of the aerosol includes the necessary container, activators, valves, subcontainers, and the like, which together may form a kit. One skilled in the art, without undue experimentation may determine preferred aerosols.

In some embodiments, the pharmaceutical compositions of the invention may be prepared by methodology well known in the pharmaceutical art. For example, a pharmaceutical composition intended to be administered by injection can be prepared by combining a compound of the invention with sterile, distilled water so as to form a solution. A surfactant may be added to facilitate the formation of a homogeneous solution or suspension. Surfactants are compounds that non-covalently interact with the compound of the invention so as to facilitate dissolution or homogeneous suspension of the compound in the aqueous delivery system.

The compounds of the invention, or their pharmaceutically acceptable salts, are administered in a therapeutically effective amount, which will vary depending upon a variety of factors including the activity of the specific compound employed; the metabolic stability and length of action of the compound; the age, body weight, general health, sex, and diet of the patient; the mode and time of administration; the rate of excretion; the drug combination; the severity of the particular disorder or condition; and the subject undergoing therapy.

Compounds of the invention, or pharmaceutically acceptable derivatives thereof, may also be administered simultaneously with, prior to, or after administration of one or more other therapeutic agents. Such combination therapy includes administration of a single pharmaceutical dosage formulation which contains a compound of the invention and one or more additional active agents, as well as administration of the compound of the invention and each active agent in its own separate pharmaceutical dosage formulation. For example, a compound of the invention and the other active agent can be administered to the patient together in a single oral dosage composition such as a tablet or capsule, or each agent administered in separate oral dosage formulations. Where separate dosage formulations are used, the compounds of the invention and one or more additional active agents can be administered at essentially the same time, i.e., concurrently, or at separately staggered times, i.e., sequentially; combination therapy is understood to include all these regimens.

In some embodiments, the concentration of the compound of structure (I) provided in the pharmaceutical compositions of the present invention is less than 100%, 90%, 80%, 70%, 60%, 50%, 40%, 30%, 20%, 19%, 18%, 17%, 16%, 15%, 14%, 13%, 12%, 11%, 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, 0.5%, 0.4%, 0.3%, 0.2%, 0.1%, 0.09%, 0.08%, 0.07%, 0.06%, 0.05%, 0.04%, 0.03%, 0.02%, 0.01%, 0.009%, 0.008%, 0.007%, 0.006%, 0.005%, 0.004%, 0.003%, 0.002%, 0.001%, 0.0009%, 0.0008%, 0.0007%, 0.0006%, 0.0005%, 0.0004%, 0.0003%, 0.0002%, or 0.0001% w/w, w/v or v/v.

In some embodiments, the concentration of the compound of structure (I) provided in the pharmaceutical compositions of the present invention is greater than 90%, 80%, 70%, 60%, 50%, 40%, 30%, 20%, 19.75%, 19.50%, 19.25% 19%, 18.75%, 18.50%, 18.25% 18%, 17.75%, 17.50%, 17.25% 17%, 16.75%, 16.50%, 16.25% 16%, 15.75%, 15.50%, 15.25% 15%, 14.75%, 14.50%, 14.25% 14%, 13.75%, 13.50%, 13.25% 13%, 12.75%, 12.50%, 12.25% 12%, 11.75%, 11.50%, 11.25% 11%, 10.75%, 10.50%, 10.25% 10%, 9.75%, 9.50%, 9.25% 9%, 8.75%, 8.50%, 8.25% 8%, 7.75%, 7.50%, 7.25% 7%, 6.75%, 6.50%, 6.25% 6%, 5.75%, 5.50%, 5.25% 5%, 4.75%, 4.50%, 4.25%, 4%, 3.75%, 3.50%, 3.25%, 3%, 2.75%, 2.50%, 2.25%, 2%, 1.75%, 1.50%, 125%, 1%, 0.5%, 0.4%, 0.3%, 0.2%, 0.1%, 0.09%, 0.08%, 0.07%, 0.06%, 0.05%, 0.04%, 0.03%, 0.02%, 0.01%, 0.009%, 0.008%, 0.007%, 0.006%, 0.005%, 0.004%, 0.003%, 0.002%, 0.001%, 0.0009%, 0.0008%, 0.0007%, 0.0006%, 0.0005%, 0.0004%, 0.0003%, 0.0002%, or 0.0001% w/w, w/v, or v/v.

In some embodiments, the concentration of the compound of structure (I) provided in the pharmaceutical compositions of the present invention is in the range from approximately 0.0001% to approximately 50%, approximately 0.001% to approximately 40%, approximately 0.01% to approximately 30%, approximately 0.02% to approximately 29%, approximately 0.03% to approximately 28%, approximately 0.04% to approximately 27%, approximately 0.05% to approximately 26%, approximately 0.06% to approximately 25%, approximately 0.07% to approximately 24%, approximately 0.08% to approximately 23%, approximately 0.09% to approximately 22%, approximately 0.1% to approximately 21%, approximately 0.2% to approximately 20%, approximately 0.3% to approximately 19%, approximately 0.4% to approximately 18%, approximately 0.5% to approximately 17%, approximately 0.6% to approximately 16%, approximately 0.7% to approximately 15%, approximately 0.8% to approximately 14%, approximately 0.9% to approximately 12%, approximately 1% to approximately 10% w/w, w/v or v/v.

In some embodiments, the concentration of the compound of structure (I) provided in the pharmaceutical compositions of the present invention is in the range from approximately 0.001% to approximately 10%, approximately 0.01% to approximately 5%, approximately 0.02% to approximately 4.5%, approximately 0.03% to approximately 4%, approximately 0.04% to approximately 3.5%, approximately 0.05% to approximately 3%, approximately 0.06% to approximately 2.5%, approximately 0.07% to approximately 2%, approximately 0.08% to approximately 1.5%, approximately 0.09% to approximately 1%, approximately 0.1% to approximately 0.9% w/w, w/v or v/v.

In some embodiments, the amount the compound of structure (I) provided in the pharmaceutical compositions of the present invention is equal to or less than 10 g, 9.5 g, 9.0 g, 8.5 g, 8.0 g, 7.5 g, 7.0 g, 6.5 g, 6.0 g, 5.5 g, 5.0 g, 4.5 g, 4.0 g, 3.5 g, 3.0 g, 2.5 g, 2.0 g, 1.5 g, 1.0 g, 0.95 g, 0.9 g, 0.85 g, 0.8 g, 0.75 g, 0.7 g, 0.65 g, 0.6 g, 0.55 g, 0.5 g, 0.45 g, 0.4 g, 0.35 g, 0.3 g, 0.25 g, 0.2 g, 0.15 g, 0.1 g, 0.09 g, 0.08 g, 0.07 g, 0.06 g, 0.05 g, 0.04 g, 0.03 g, 0.02 g, 0.01 g, 0.009 g, 0.008 g, 0.007 g, 0.006 g, 0.005 g, 0.004 g, 0.003 g, 0.002 g, 0.001 g, 0.0009 g, 0.0008 g, 0.0007 g, 0.0006 g, 0.0005 g, 0.0004 g, 0.0003 g, 0.0002 g, or 0.0001 g.

In some embodiments, the amount of the compound of structure (I) provided in the pharmaceutical compositions of the present invention is more than 0.0001 g, 0.0002 g, 0.0003 g, 0.0004 g, 0.0005 g, 0.0006 g, 0.0007 g, 0.0008 g, 0.0009 g, 0.001 g, 0.0015 g, 0.002 g, 0.0025 g, 0.003 g, 0.0035 g, 0.004 g, 0.0045 g, 0.005 g, 0.0055 g, 0.006 g, 0.0065 g, 0.007 g, 0.0075 g, 0.008 g, 0.0085 g, 0.009 g, 0.0095 g, 0.01 g, 0.015 g, 0.02 g, 0.025 g, 0.03 g, 0.035 g, 0.04 g, 0.045 g, 0.05 g, 0.055 g, 0.06 g, 0.065 g, 0.07 g, 0.075 g, 0.08 g, 0.085 g, 0.09 g, 0.095 g, 0.1 g, 0.15 g, 0.2 g, 0.25 g, 0.3 g, 0.35 g, 0.4 g, 0.45 g, 0.5 g, 0.55 g, 0.6 g, 0.65 g, 0.7 g, 0.75 g, 0.8 g, 0.85 g, 0.9 g, 0.95 g, 1 g, 1.5 g, 2 g, 2.5, 3 g, 3.5, 4 g, 4.5 g, 5 g, 5.5 g, 6 g, 6.5 g, 7 g, 7.5 g, 8 g, 8.5 g, 9 g, 9.5 g, or 10 g.

In some embodiments, the amount of the compound of structure (I) provided in the pharmaceutical compositions of the present invention is in the range of 0.0001-10 g, 0.0005-9 g, 0.001-8 g, 0.005-7 g, 0.01-6 g, 0.05-5 g, 0.1-4 g, 0.5-4 g, or 1-3 g.

It will also be appreciated by those skilled in the art that, in the processes for preparing compounds of structure (I) described herein, the functional groups of intermediate compounds may need to be protected by suitable protecting groups. Such functional groups include hydroxy, amino, mercapto and carboxylic acid. Suitable protecting groups for hydroxy include trialkylsilyl or diarylalkylsilyl (for example, t-butyldimethylsilyl, t-butyldiphenylsilyl or trimethylsilyl), tetrahydropyranyl, benzyl, and the like. Suitable protecting groups for amino, amidino and guanidino include t-butoxycarbonyl, benzyloxycarbonyl, and the like. Suitable protecting groups for mercapto include —C(O)—R″ (where R″ is alkyl, aryl or arylalkyl), p-methoxybenzyl, trityl and the like. Suitable protecting groups for carboxylic acid include alkyl, aryl or arylalkyl esters. Protecting groups may be added or removed in accordance with standard techniques, which are known to one skilled in the art and as described herein. The use of protecting groups is described in detail in Green, T. W. and P. G. M. Wutz, Protective Groups in Organic Synthesis (1999), 3rd Ed., Wiley. As one of skill in the art would appreciate, the protecting group may also be a polymer resin such as a Wang resin, Rink resin or a 2-chlorotrityl-chloride resin.

It will also be appreciated by those skilled in the art, although such protected derivatives of compounds of this invention may not possess pharmacological activity as such, they may be administered to a mammal and thereafter metabolized in the body to form compounds of the invention which are pharmacologically active. Such derivatives may therefore be described as “prodrugs”. All prodrugs of compounds of this invention are included within the scope of the invention.

Furthermore, all compounds of the invention which exist in free base or acid form can be converted to their pharmaceutically acceptable salts by treatment with the appropriate inorganic or organic base or acid by methods known to one skilled in the art. Salts of the compounds of the invention can be converted to their free base or acid form by standard techniques.

Compounds of structure (I) can be prepared by addition of a phosphate group to one of the three free hydroxyls of alvocidib. The alvocidib parent compound (and salts and solvates thereof) can be purchased from commercial sources or prepared according to methods known in the art, for example as described in U.S. Pat. Nos. 6,136,981; 6,225,473; 6,406,912; 6,576,647; and 6,821,990; the full disclosures of which are herein incorporated by reference in their entireties.

The following General Reaction Scheme illustrates a method of making compounds of this invention, i.e., compound of structure (I):

or a stereoisomer, tautomer or pharmaceutically acceptable salt thereof, wherein R¹, R² and R³ are as defined above. It is understood that one skilled in the art may be able to make these compounds by similar methods or by combining other methods known to one skilled in the art. It is also understood that one skilled in the art would be able to make, in a similar manner as described below, other compounds of structure (I) not specifically illustrated below by using the appropriate starting components and modifying the parameters of the synthesis as needed. In general, starting components may be obtained from sources such as Sigma Aldrich, Lancaster Synthesis, Inc., Maybridge, Matrix Scientific, TCI, and Fluorochem USA, etc. or synthesized according to sources known to those skilled in the art (see, for example, Advanced Organic Chemistry: Reactions, Mechanisms, and Structure, 5th edition (Wiley, December 2000)) or prepared as described in this invention.

As shown in General Reaction Scheme 1, alvocidib HCl salt A is first reacted with an appropriately protected chlorophosphate (i.e., B, wherein R is a protecting group, such as ethyl). Deprotection then provides the desired compound of structure (I). It will be apparent to one of ordinary skill in the art that compounds of structure (I) having a single phosphate at any one of the three hydroxyl groups of alvocidib can be prepared according to the above scheme, and the desired regioisomer separated by usual techniques, such as chromatography. Protecting group strategies for optimizing the yield of the desired regioisomer will also be apparent to one of ordinary skill in the art.

Methods

In various embodiments, the invention provides a method for treating a disease in a mammal in need thereof by administration of a compound of structure (I), or a pharmaceutical composition comprising the same, to the mammal. In some specific embodiments, the method is for treating a disease associated with overexpression of a cyclin-dependent kinase (CDK) in a mammal in need thereof, the method comprising administering a therapeutically effective amount of any of the foregoing compounds of structure (I), or a pharmaceutical composition comprising the same, to the mammal.

In some more embodiments, the disease is cancer, for example a hematologic cancer. In some of these embodiments, the hematologic cancer is selected from acute myelogenous leukemia (AML), multiple myeloma, follicular lymphoma, acute lymphoblastic leukemia (ALL), chronic lymphocytic leukemia (CLL) and non-Hodgkin's lymphoma. In other embodiments, the hematological cancer is acute myelogenous leukemia (AML). In other different embodiments, the hematologic cancer is chronic lymphocytic leukemia (CLL). In still more different embodiments, the hematologic cancer is myelodysplasic syndrome (MDS).

In some other specific embodiments of the foregoing methods, the method comprises orally administering the compound of structure (I), or the pharmaceutical composition comprising the same, to the mammal.

In addition to the above exemplary diseases, a wide variety of cancers, including solid tumors and leukemias (e.g., acute myeloid leukemia) are amenable to the methods disclosed herein. Types of cancer that may be treated in various embodiments include, but are not limited to: adenocarcinoma of the breast, prostate, and colon; all forms of bronchogenic carcinoma of the lung; myeloid; melanoma; hepatoma; neuroblastoma; papilloma; apudoma; choristoma; branchioma; malignant carcinoid syndrome; carcinoid heart disease; and carcinoma (e.g., Walker, basal cell, basosquamous, Brown-Pearce, ductal, Ehrlich tumor, Krebs 2, merkel cell, mucinous, non-small cell lung, oat cell, papillary, scirrhous, bronchiolar, bronchogenic, squamous cell, and transitional cell). Additional types of cancers that may be treated include: histiocytic disorders; leukemia; histiocytosis malignant; Hodgkin's disease; immunoproliferative small; non-Hodgkin's lymphoma; plasmacytoma; reticuloendotheliosis; melanoma; chondroblastoma; chondroma; chondrosarcoma; fibroma; fibrosarcoma; giant cell tumors; histiocytoma; lipoma; liposarcoma; mesothelioma; myxoma; myxosarcoma; osteoma; osteosarcoma; chordoma; craniopharyngioma; dysgerminoma; hamartoma; mesenchymoma; mesonephroma; myosarcoma; ameloblastoma; cementoma; odontoma; teratoma; thymoma; trophoblastic tumor. Further, the following types of cancers are also contemplated as amenable to treatment: adenoma; cholangioma; cholesteatoma; cyclindroma; cystadenocarcinoma; cystadenoma; granulosa cell tumor; gynandroblastoma; hepatoma; hidradenoma; islet cell tumor; Leydig cell tumor; papilloma; sertoli cell tumor; theca cell tumor; leimyoma; leiomyosarcoma; myoblastoma; myomma; myosarcoma; rhabdomyoma; rhabdomyosarcoma; ependymoma; ganglioneuroma; glioma; medulloblastoma; meningioma; neurilemmoma; neuroblastoma; neuroepithelioma; neurofibroma; neuroma; paraganglioma; paraganglioma nonchromaffin. The types of cancers that may be treated also include, but are not limited to, angiokeratoma; angiolymphoid hyperplasia with eosinophilia; angioma sclerosing; angiomatosis; glomangioma; hemangioendothelioma; hemangioma; hemangiopericytoma; hemangiosarcoma; lymphangioma; lymphangiomyoma; lymphangiosarcoma; pinealoma; carcinosarcoma; chondrosarcoma; cystosarcoma phyllodes; fibrosarcoma; hemangiosarcoma; leiomyosarcoma; leukosarcoma; liposarcoma; lymphangiosarcoma; myosarcoma; myxosarcoma; ovarian carcinoma; rhabdomyosarcoma; sarcoma; neoplasms; nerofibromatosis; and cervical dysplasia.

The compounds of the invention are effective over a wide dosage range. For example, in the treatment of adult humans, dosages from 0.01 to 1000 mg, from 0.5 to 100 mg, from 1 to 50 mg per day, and from 5 to 40 mg per day are examples of dosages that are used in some embodiments. An exemplary dosage is 10 to 30 mg per day. The exact dosage will depend upon the route of administration, the form in which the compound is administered, the subject to be treated, the body weight of the subject to be treated, and the preference and experience of the attending physician.

In some embodiments, a compound of the invention is administered in a single dose. A single dose of a compound of the invention may also be used for treatment of an acute condition.

In some embodiments, a compound of the invention is administered in multiple doses. In some embodiments, dosing is about once, twice, three times, four times, five times, six times, or more than six times per day. In other embodiments, dosing is about once a month, once every two weeks, once a week, or once every other day. In another embodiment a compound of the invention and another agent are administered together about once per day to about 6 times per day. In another embodiment the administration of a compound of the invention and an agent continues for less than about 7 days. In yet another embodiment the administration continues for more than about 6, 10, 14, 28 days, two months, six months, or one year. In some cases, continuous dosing is achieved and maintained as long as necessary.

Administration of the compounds of the invention may continue as long as necessary. In some embodiments, a compound of the invention is administered for more than 1, 2, 3, 4, 5, 6, 7, 14, or 28 days. In some embodiments, a compound of the invention is administered for less than 28, 14, 7, 6, 5, 4, 3, 2, or 1 day. In some embodiments, a compound of the invention is administered chronically on an ongoing basis, e.g., for the treatment of chronic effects.

In some embodiments, the compounds of the invention are administered in dosages. Due to intersubject variability in compound pharmacokinetics, individualization of dosing regimen is provided in certain embodiments. Dosing for a compound of the invention may be found by routine experimentation in light of the instant disclosure and/or can be derived by one of ordinary skill in the art.

EXAMPLES Example 1 Preparation of Representative Phosphate Prodrug (IB′)

2-(2-chlorophenyl)-5-hydroxy-8-(3-hydroxy-1-methylpiperidin-4-yl)-4-oxo-4H-chromen-7-yl diethyl phosphate

A suspension of alvocidib HCl (2 g, 4.56 mmol, 1 eq.) in 1,2-dichloroethane (40 mL) was cooled to 0° C. To this solution, triethylamine (1.9 mL, 13.7 mmol, 3 eq.) followed by diethylchlorophosphate (0.78 g, 4.56 mmol, 1 eq.) were added. The reaction mixture was stirred at 0° C. for 30-45 min. The reaction mixture was then poured onto ice and extracted with dichloromethane (3×25 mL). The combined organic layers were dried over anhydrous Na₂SO₄ and concentrated to get a crude residue. The crude residue was purified by flash column chromatography using 10-15% methanol in dichloromethane to afford 2-(2-chlorophenyl)-5-hydroxy-8-(3-hydroxy-1-methylpiperidin-4-yl)-4-oxo-4H-chromen-7-yl diethyl phosphate (550 mg, 1.02 mmol; 22%).

LCMS: Column: XBridge C8 (50×4.6 mm×3.5 μm); Mobile phase: A: 10 mM NH₄CO₃ in H₂O; B: ACN; RT: 5.97; Purity: (Max: 67.63); M+H: 538.0.

2-(2-chlorophenyl)-5-hydroxy-8-(3-hydroxy-1-methylpiperidin-4-yl)-4-oxo-4H-chromen-7-yl dihydrogen phosphate (IB′)

To a solution of 2-(2-chlorophenyl)-5-hydroxy-8-(3-hydroxy-1-methylpiperidin-4-yl)-4-oxo-4H-chromen-7-yl diethyl phosphate (0.55 g, 1.02 mmol, 1 eq.) in dichloromethane (4 mL) at 0° C., trimethylsilylbromide (2.0 mL, 15.1 mmol, 15 eq.) was added. The reaction mixture was then heated at 36° C. under sealed condition for 20 h. The reaction mixture was evaporated. The crude residue obtained was purified by preparative HPLC to afford 2-(2-chlorophenyl)-5-hydroxy-8-(3-hydroxy-1-methylpiperidin-4-yl)-4-oxo-4H-chromen-7-yl dihydrogen phosphate (35 mg; 0.073 mmol; 7%).

LCMS: Column: XBridge C8 (50×4.6 mm×3.5 μm); Mobile phase: A: 10 mM NH₄CO₃ in H₂O; B: ACN; RT: 3.11; Purity: (Max: 93.56); M+H: 482.0.

HPLC: Column: XBridge C8 (50×4.6 mm×3.5 μm); Mobile phase: A: 0.1% TFA in H₂O; B: ACN; RT: 2.55; Purity: (Max: 96.39; 254 nm: 96.57).

1HNMR (DMSO-d₆-D₂O exchange): δ 7.84 (d, J=7.20 Hz, 1H), 7.71-7.70 (m, 1H), 7.65-7.62 (m, 1H), 7.59-7.55 (m, 1H), 7.07 (s, 1H), 6.62 (s, 1H), 4.12 (s, 1H), 3.60-3.54 (m, 1H), 3.30-3.26 (m, 3H), 3.13-3.11 (m, 2H), 2.71 (s, 3H), 1.83-1.80 (m, 1H).

Example 2 Pharmacokinetic Profile of Alvocidib Prodrugs

The following compounds were prepared and their pharmacokinetic profile determined and compared to the pharmacokinetic profile of compound (IB′) as described below.

Compounds were prepared and administered to CD-1 mice intravenously (IV) or orally (PO) as summarized in Table 1. The plasma concentration of the alvocidib parent compound was determined at various time intervals (Table 2) and the pharmacokinetic parameters calculated (Table 3). Compounds E and F did not convert to alvocidib in vivo (i.e., no alvocidib was detected in plasma samples of mice treated with these compounds), and their pharmacokinetic parameters were not further investigated. As can be seen in Table 3, the bioavailability of compound (IB′) is superior that of the parent alvocidib compound (A) and the two diphosphate compounds (C and D).

TABLE 1 Design of Pharmacokinetic Profiling Experiments IV PO Dose (mg/kg) 1 10 Dosing volume 2 10 (ml/kg) Formulation 0.5 1 Conc (mg/ml) Formulation Details IV Formulation N-methyl pyrollidone:Ethanol:PEG200:NS (2:10:30:58) PO Tween80:Ethanol:PEG400:water (2:10:30:58) Formulation Type of PK Planed Species Mouse Strain ICR-CD1 Sex Male Age/Body ~7-8 weeks/25-30 g weight: Groups IV: 1 gr; PO: 1 gr No of animals/ 3/3 group IV Dosing Tail vein PO Dosing oral gvage Sample Type Plasma Blood Saphenous vein collection Anti- 0.2% K2 EDTA coagulant used

TABLE 2 Plasma Concentration of Alvocidib Alvocidib Plasma Concentrations (ng/ml) Time A C D (IB′) (hr) IV PO IV PO IV PO IV PO 0.083 427.9 ± — 30.1 ± — 9.9 ± — 366.8 ± — 26.5 6.5 8.0 9.9 0.25 335.7 ± 1491 ± 53.4 ± 7.5 ± 31.4 ± 5.2 ± 265.1 ± 1868.7 ± 64.1 211.0 11.0 4.2 17.0 4.7 36.4 51.1 0.5 263.9 ± 1167.2 ± 62.1 ± 17.9 ± 43.8 ± 14.4 ± 183.6 ± 1880.5 ± 48.2 186.0 2.3 1.0 11.0 1.8 12.5 119.1 1.0 136.4 ± 675.5 ± 33.2 ± 28.5 ± 45.3 ± 39.3 ± 105.0 ± 1338.5 ± 41.9 139.7 15.1 2.3 7.2 1.9 17.8 188.8 2.0 52.5 ± 333.7 ± 19.8 ± 46.0 ± 17.0 ± 59.5 ± 40.2 ± 740.5 ± 8.1 94.5 5.34 3.8 5.4 5.9 1.9 147.4 4.0 28.9 ± 304.8 ± 13.5 ± 36.8 ± 9.4 ± 55.5 ± 16.8 ± 388.3 ± 6.3 29.5 2.0 1.7 0.7 3.6 1.1 35.7 6.0 13.5 ± 341.3 ± 5.9 ± 100 ± 4.4 ± 108.3 ± 7.22 ± 470.7 ± 3.3 53.3 0.4 4.5 0.2 1.4 0.3 18.4 8.0 6.7 ± 241.9 ± 3.6 ± 76.8 ± 2.2 ± 93.1 ± 2.9 ± 252.5 ± 0.4 24.9 0.6 3.3 1.6 3.7 0.4 31.0 24.0 n.e. 36.7 ± n.e. 2.0 ± n.e. n.e. n.e. 21.7 ± 11.1 0.3 17.5 Note: Results are expressed in Mean ± SD, n = 3animals/group n.e. = not evaluated

TABLE 3 Pharmacokinetic Profiles Mice PK summary Table (Dose: IV-1 mg/kg & PO-10 mg/kg) PK A C D (IB′) Parameters IV PO IV PO IV PO IV PO C_(max) — 1492.0 ± — 100.1 ± — 108.3 ± — 1922.7 ± (ng/mL) 211.0 4.5 1.4 72.1 T_(max) — 0.25 ± — 6.0 ± — 6.0 ± — 0.33 ± (h) 0.0 0.1 0.1 0.14 AUC_(Last) 498.0 ± 5034.1 ± 132.8 ± 776.6 ± 109.0 ± 545.8 ± 363.6 ± 6619.6 ± (ng*h/mL) 46.0 145.6 14.8 32.8 12.0 11.9 18.0 631.7 AUC_(0-∞) 517.0 ± 5341.1 ± 144.6 ± 785.6 ± 114.3 ± — 370.2 ± — (ng*h/mL) 47.0 274.2 13.4 33.5 7.0 19.0 Clearance 1.9 ± — 7.0 ± — 8.8 ± — 2.7 ± — (L/h/Kg) 0.2 0.7 0.5 0.14 Vd 5.5 ± — 22.0 ± — 22.0 ± — 6.1 ± — (L/Kg) 1.2 5.1 13.1 0.0 Vd_(SS) 3.8 ± — 21.6 ± — 23.5 ± — 4.2 ± — (L/Kg) 0.6 4.4 7.4 0.1 Half life 2.0 ± 5.7 ± 2.2 ± 3.1 ± 1.72 ± — 1.57 ± 4.4 ± (h) 0.4 0.7 0.5 0.1 0.9 0.08 1.3 Bioavail. 102 ± 59.0 ± 50.5 ± — 182.3 ± (% F) 11.7 8.0 4.7 20.0 NOTE: RESULTS ARE EXPRESSED IN MEAN ± SD, N = 3ANIMALS/GROUPEXAMPLE 3

Kinetic Solubility Profiles

The aqueous kinetic solubility of compound IB′ was determined across a broad pH range (i.e. pH 2.2-pH 8.7) and compared to the aqueous kinetic solubility of alvocidib for the same pH range. The solubility of compound IB′ was found to be in excess of 1 mg/mL at the lowest pH tested (pH 2.2), rising to above 5 mg/mL at pH 6.8 and pH 8.7. By comparison, the solubility of alvocidib is above 1 mg/mL at pH 2.2 and pH 4.5 but drops to 0.02 mg/mL at pH 6.8 and pH 8.7.

TABLE 4 Kinetic Solubility Profiles Concentration Solubility (mg/mL) Compound tested (mg/mL) pH 2.2 pH 4.5 pH 6.8 pH 8.7 Alvocidib 1 1.05 0.95 0.02 0.00 5 4.82 1.99 0.02 0.02 10 4.38 1.25 0.02 0.02 Compound IB′ 1 1.07 1.10 1.09 1.09 5 1.90 2.33 5.56 5.65 10 1.52 1.81 9.48 9.31

Example 4 Plasma Stability Profiles

The plasma stability of compound IB′ was determined using plasma from four species. Results for mouse, rat, dog and human are shown in Tables 5, 6, 7 and 8 respectively. Alvocidib and flumazenil were used as controls. In mouse, rat and human plasma, compound IB′ maintained 100% stability after 5 hour incubation. In dog plasma, approximately 90% of compound IB′ remained after 5 hours. By comparison, alvocidib maintained 100% stability across all four species after 5 hours, and flumazenil was unstable in mouse and rat plasma.

TABLE 5 Mouse Plasma Stability Profiles % Remaining Compound 0 hours 0.5 hours 1 hour 2 hours 3 hours 4 hours 5 hours Flumazenil 100.00 29.96 10.21 1.56 0.39 0.20 0.07 Alvocidib 100.00 93.58 103.12 97.19 117.38 115.72 111.28 Compound IB′ 100.00 88.48 89.83 97.71 99.61 100.46 100.20

TABLE 6 Rat Plasma Stability Profiles % Remaining Compound 0 hours 0.5 hours 1 hour 2 hours 3 hours 4 hours 5 hours Flumazenil 100.00 42.23 16.13 1.69 0.23 0.00 0.00 Alvocidib 100.00 93.12 90.20 99.31 98.69 92.57 117.71 Compound IB′ 100.00 97.39 94.60 100.04 107.48 100.20 99.78

TABLE 7 Dog Plasma Stability Profiles % Remaining Compound 0 hours 0.5 hours 1 hour 2 hours 3 hours 4 hours 5 hours Flumazenil 100.00 91.80 92.00 100.99 115.10 99.44 100.53 Alvocidib 100.00 96.41 89.16 105.76 105.84 97.65 100.40 Compound IB′ 100.00 83.66 94.53 112.61 99.16 93.91 90.24

TABLE 8 Human Plasma Stability Profiles % Remaining Compound 0 hours 0.5 hours 1 hour 2 hours 3 hours 4 hours 5 hours Flumazenil 100.00 96.56 90.83 92.41 117.98 95.32 94.63 Alvocidib 100.00 92.61 93.54 93.29 111.62 100.25 104.65 Compound IB′ 100.00 96.32 88.01 104.22 102.59 94.36 100.26

Example 5 Pharmacokinetics in Sprague Dawley Rats

The plasma concentrations of alvocidib produced by oral and intravenous (IV) administration of compound IB′ and of absorbed compound IB′ itself, were determined in male Sprague Dawley (SD) rats (see FIG. 1). Plasma samples were taken at 8 time-points (IV) or 7 time points (oral) over a 24 hour period following a single dose of compound IB′ (3 animals per group). The calculated pharmacokinetic parameters are shown in Table 9 and Table 10. Both IV and oral administration of compound IB′ led to significant exposure of alvocidib. Administered intravenously, compound IB′ (1 mg/kg) was metabolized to alvocidib with a C₀ of 270.3 ng/mL which was eliminated with a half-life of 1.6 hours. Administered orally, compound IB′ (10 mg/kg) was metabolized to alvocidib with a C_(max) of 178.6 ng/mL and a T_(max) of 2.92 hours, which was eliminated with a half-life of 4.4 hours. The bioavailability of alvocidib (99.03%) was calculated from the ratio of the area under the curve (AUC) for alvocidib produced from oral and IV administration of compound IB′. The plasma samples were also analyzed for the presence of compound IB′. The plasma concentrations of compound IB′ in SD rats are also shown in FIG. 1 and Table 11. For both IV and oral administration in SD rats, plasma levels of compound IB′ dropped below quantitative levels at 2 hours post dosing.

TABLE 9 Pharmacokinetic Parameters for Alvocidib Following Intravenous Administration of Compound IB′ in Sprague Dawley Rats Parameter Value SD C₀ (ng/mL) 270.3 48.6 AUC_(in) (hr · ng/mL) 135.6 21.1 AUC_(0-t) (hr · ng/mL) 129.9 22.8 AUC_(in)/AUC_(0-t) (%) 104.6 2.3 V_(d) (L/kg) 17.50 1.93 CL_(p) (L/hr/kg) 7.5 1.1 V_(d,ss) (L/kg) 17.71 10.08 MRT_(in) (hr) 2.5 1.8 t_(1/2) (hr) 1.6 0.4

TABLE 10 Pharmacokinetic Parameters for Alvocidib Following Oral Administration of Compound IB′ in Sprague Dawley Rats Parameter Value SD C_(max) (ng/mL) 178.6 47 T_(max) (hr) 2.92 4.4 AUC_(in) (hr · ng/mL) 1280.5 194 AUC_(0-t) (hr · ng/mL) 1241.2 185 AUC_(in)/AUC_(0-t) (%) 103.2 0.8 Bioavailability (%) 99.03 30.2 t_(1/2) (hr) 4.40 0.5

TABLE 11 Plasma Concentrations of Compound IB following Intravenous or Oral Administration of Compound IB′ in Sprague Dawley Rats Time (hr) IV (ng/mL) SD PO (ng/mL) SD 0.083 429.6 144.0 # # 0.25 82.0 6.6 30.0 9.7 0.50 24.6 4.2 20.4 6.6 1.00 9.3 2.8  9.3 0.4 2.00 BQL — BQL — 4.00 BQL — BQL — 6.00 BQL — BQL — 8.00 BQL — BQL — 24.00 BQL — BQL — # not measured BQL = below quantitation limit

Example 6 Maximum Tolerated Acute Dose in Mice

Acute (i.e. single dose) toxicology studies were performed in mice. Acute studies were performed in female SHO SCID mice using three animals per treatment group. Animals were treated with a single dose of compound IB′ at 45, 30, 15, or 7.5 mg/kg. For comparison, additional animals were treated with alvocidib at the same dose levels. Body weight measurements following oral dosing (FIG. 2A-B) and intravenous (IV) dosing (FIG. 2C-D) were used, along with mortality and clinical observations to determine the maximum tolerated acute dose (MTD_(acute)).

The results from the acute study determined that the MTD_(acute) of compound IB′, dosed orally, is 15 mg/kg. The MTD_(acute) of compound IB′, dosed intravenously, is 15 mg/kg. Body weight loss and increased lethargy were observed in animals dosed at 30 mg/kg and 45 mg/kg. In animals dosed orally at 45 mg/kg, one animal died on day two and one animal died on day three. In animals dosed orally at 30 mg/kg, one animal died on day four. In animals dosed intravenously at 45 mg/kg, two animals died on day two. In animals dosed intravenously at 30 mg/kg, one animal died on day three.

The acute MTD_(acute) of alvocidib, when dosed orally, is 15 mg/kg. The MTD_(acute) of alvocidib, dosed intravenously, is 7.5 mg/kg. Some body weight loss, increased lethargy, and animal deaths were observed in animals dosed with alvocidib at both the 30 and 45 mg/kg dose levels.

Body weight loss was observed in surviving animals at 45 mg/kg and 30 mg/kg oral dosing levels of compound IB′, peaking at 17% in the 30 mg/kg group. Body weight loss in surviving animals dosed intravenously peaked at 12%.

No overt toxicity was observed in mice dosed orally or intravenously at 15 mg/kg or 7.5 mg/kg. Minor body weight loss peaking at 3.3% in the 15 mg/kg intravenous dosing group was attributed to normal body weight fluctuation in test animals.

Compound IB′ is better tolerated (MTD_(acute)=15 mg/kg) in mice when dosed intravenously compared to alvocidib (MTD_(acute)=7.5 mg/kg).

Example 7 Maximum Tolerated Repeated Dose Schedule in Mice

Repeat dose toxicology studies were performed in female SHO SCID mice using 3 animals per treatment group. Animals were treated with five daily doses of compound IB′ at 15, 7.5, or 2.5 mg/kg, and were observed for five additional days following the dosing regimen. For comparison, additional animals were treated with alvocidib at the same dose levels and the same dosing/observation schedule. Body weight measurements of animals treated by oral (see FIG. 3A-B) and intravenous (see FIG. 3C-D) dosing over the course of the 5-day repeat dosing period and subsequent 5-day observation period, along with mortality and clinical observations, were used to determine the maximum tolerated dosing schedule (MTD_(repeat)).

The results from the 5-day repeat-dose study determined that the MTD_(repeat) of compound IB, dosed orally, is 7.5 mg/kg. The MTD_(repeat) of compound IB′, dosed intravenously, is 15 mg/kg. Body weight loss was observed in animals dosed orally at 15 mg/kg. In animals dosed orally at 15 mg/kg, one animal died on day 5, and one animal died on day 7.

For comparison, the MTD_(repeat) determined for alvocidib, when dosed orally, was 7.5 mg/kg. The MTD_(repeat) determined for alvocidib, when dosed intravenously, was 7.5 mg/kg. Lethargy, body weight loss, and deaths were observed at the 15 mg/kg dosing levels for both oral and intravenous dosing with alvocidib.

Body weight loss was observed in surviving animals at the 15 mg/kg oral dosing level with compound IB′, which peaked at 12%. No overt toxicity was observed in animals dosed orally at 7.5 mg/kg or 2.5 mg/kg, or in animals dosed at any dose level attempted when administered intravenously.

Compound IB′ is better tolerated (MTD_(repeat)=15 mg/kg) in mice when dosed intravenously compared to alvocidib (MTD_(repeat)=7.5 mg/kg).

Example 8 Maximum Tolerated Acute Dose in Rats

Acute (i.e. single dose) toxicology studies were performed in rats. Acute studies were performed in female Sprague Dawley rats using three animals per treatment group. Animals were treated with a single dose of compound IB′ at 36, 18, 9, or 4.5 mg/kg. For comparison, additional animals were dosed with 18, 9, or 4.5 mg/kg alvocidib. Body weight measurements following oral dosing (see FIG. 4A), along with mortality, clinical observations, food consumption (see FIG. 4B), and complete blood counts (CBCs; see Table 12) were used to determine the maximum tolerated acute dose (MTD_(acute)).

The results from the acute study determined that the MTD_(acute) of compound IB′ in rats is 18 mg/kg. Diarrhea, body weight loss and increased lethargy were observed in animals dosed with compound IB at 36 mg/kg. At this dose level, one animal died on day three, one animal died on day four, and one animal died on day 5. Deaths were not observed in any other treatment group.

Body weight loss was observed in treated animals, preceding death, reaching 13.1% in animals treated at the 36 mg/kg dose level with compound IB′ (see FIG. 4A). This body weight loss was accompanied by significant diarrhea, and increased lethargy in these animals. No overt toxicity, including body weight change or diarrhea, was observed in rats dosed at 18, 9, or 4.5 mg/kg with compound IB′. In comparison, animals dosed with 18 mg/kg alvocidib did show signs of diarrhea. In addition, abnormal food consumption patterns were observed with 18 mg/kg dosing of alvocidib that were not observed with the compound IB′ treated animals at the same dosage level.

Abnormal CBCs were observed in some animals (Table 12). Specifically, platelet counts were outside the normal range for the vehicle and 9 mg/kg dosage of compound IB′, and 4.5 mg/kg alvocidib dose. No consistent dose-dependent trend was observed in the surviving, treated animals. Slightly reduced red and white blood cell counts were observed at the 18 mg/kg dose level for compound IB′. However, slightly elevated counts were also observed in some untreated animals as well. The high variability of these results was attributed to inter-animal variation, and not drug-dependent mechanisms. As animals treated with 36 mg/kg of compound IB′ expired overnight, CBCs were not available.

Based on the data above, the rat oral MTD_(acute) of compound IB′ was found to distinguish its tolerability profile versus that of alvocidib as the no observable adverse effect level (NOAEL) was found to be 18 mg/kg for compound IB′ and 9 mg/kg for alvocidib.

TABLE 12 Blood Counts of Rats Treated With a Single Dose of Compound IB RBC MCV HCT MCH MCHC RDWA PLT HGB WBC (10⁶/μL) (fL) (%) (pg) (g/dL) (fL) (10³/μL) (g/dL) (10³/μL) Vehicle 7.8 53.1 41.5 19.5 36.8 15.7 34.3 174.3 15.2 36 mg/kg — — — — — — — — — compound IB′ 18 mg/kg 5.9 53.5 31.2 19.6 36.6 15.7 33.9 201.3 11.4 compound IB′ 9 mg/kg 8.0 53.3 42.7 19.5 36.6 15.9 35.0 112.7 15.6 compound IB′ 4.5 mg/kg 9.1 54.8 49.9 19.7 35.9 16.2 37.1 319.3 17.9 compound IB′ 18 mg/kg 8.8 53.8 47.3 19.3 35.9 16.1 36.1 376.0 16.9 alvocidib 9 mg/kg 8.7 54.0 47.1 19.3 35.7 16.2 36.3 334.7 16.8 alvocidib 4.5 mg/kg 8.3 52.7 43.6 18.7 35.4 16.0 34.7 147.0 15.4 alvocidib

Example 9 Mouse Xenograft Efficacy Study

The in vivo activity of compound IB′ was determined in a MV4-11 mouse xenograft model of acute myeloid leukemia (AML). Injection of 8×10⁶ MV4-11 cells/mouse was followed by growth of tumors to approximately 100 mm³. After tumors reached the appropriate size, mice were randomized into the following treatment groups: Vehicle, compound IB′ (7.5 mg/kg, qdx5x3), compound IB′ (2.5 mg/kg, qdx5x3), compound IB′ (0.1 mg/kg, qdx5x3) and compound IB (7.5 mg/kg, q7dx3). Vehicle and compound IB′ were administered orally, except in the last arm of compound IB′ (7.5 mg/kg, q7dx3), which was dosed intravenously. Treatment resulted in significant tumor growth inhibition (% TGI; see FIGS. 5A-B and Table 13).

TABLE 13 Tumor Growth Inhibition for Mouse Xenograft Efficacy Study Tumor Growth Dosage of Compound IB′ Inhibition (%) Vehicle (i.e. no compound IB′) 0  7.5 mg/kg 69 2..5 mg/kg 12  7.5 mg/kg, q7dx3 74

Example 10 Mouse Xenograft Pharmacodynamic Study

The in vivo pharmacodynamic activity of compound IB′ was determined in a MV4-11 mouse xenograft model of AML (FIG. 6A-B). Injection of 8×10⁶ cells/mouse was followed by growth of tumors to approximately 100 mm³. After tumors reached an appropriate size, mice were randomized into the following treatment groups: Vehicle, compound IB′ (2.5 mg/kg), compound IB′ (0.5 mg/kg), compound IB′ (0.1 mg/kg), compound IB′ (0.02 mg/kg). Mice were administered a single treatment dose and tumors were harvested 48 hours post-treatment. MCL-1 protein levels were assessed on harvested tumors using standard polyacrylamide gel electrophoresis and immunoblotting technique (FIG. 6A). Treatment resulted in reduction of MCL-1 protein expression (see FIG. 6B and Table 14 below).

TABLE 14 Reduction of MCL-1 Protein Expression Reduction of MCL-1 Dosage of Compound IB′ Expression (%) Vehicle (i.e. no compound IB′) 0.0 2.5 mg/kg 54 0.5 mg/kg 61 0.1 mg/kg 46 0.02 mg/kg  0.0

All of the U.S. patents, U.S. patent application publications, U.S. patent applications, foreign patents, foreign patent applications and non-patent publications referred to in this specification, including U.S. Provisional Patent Application Ser. No. 62/163,188, filed May 18, 2015, are incorporated herein by reference, in their entirety to the extent not inconsistent with the present description.

From the foregoing it will be appreciated that, although specific embodiments of the invention have been described herein for purposes of illustration, various modifications may be made without deviating from the spirit and scope of the invention. Accordingly, the invention is not limited except as by the appended claims. 

1-15. (canceled)
 16. A method for treating a disease associated with overexpression of a cyclin-dependent kinase (CDK) in a mammal in need thereof, the method comprising administering a therapeutically effective amount of a compound of structure (I), or a pharmaceutical composition comprising the compound of structure (I), to the mammal, wherein the compound of structure (I) has following structure:

or a stereoisomer, tautomer or pharmaceutically acceptable salt thereof, wherein: i) R¹ is —P(═O)(OH)₂, and R² and R³ are each H; ii) R² is —P(═O)(OH)₂, and R¹ and R³ are each H; or iii) R³ is —P(═O)(OH)₂, and R¹ and R² are each H.
 17. The method of claim 16, wherein the disease is cancer.
 18. The method of claim 17, wherein the cancer is a hematologic cancer.
 19. The method of claim 18, wherein the hematologic cancer is selected from acute myelogenous leukemia (AML), multiple myeloma, follicular lymphoma, acute lymphoblastic leukemia (ALL), chronic lymphocytic leukemia (CLL) and non-Hodgkin's lymphoma.
 20. The method of claim 19, wherein the hematological cancer is acute myelogenous leukemia (AML).
 21. The method of claim 19, wherein the hematologic cancer is chronic lymphocytic leukemia (CLL).
 22. The method of claim 18, wherein the hematologic cancer is myelodysplasic syndrome (MDS).
 23. The method of claim 16, wherein the method comprises orally administering the compound of structure (I), or the pharmaceutical composition comprising the compound of structure (I), to the mammal.
 24. The method of claim 16, wherein the compound of structure (I) has the following structure (I′):


25. The method of claim 16, wherein the compound of structure (I) has the following structure (IA):


26. The method of claim 16, wherein the compound of structure (I) has the following structure (IA′):


27. The method of claim 16, wherein the compound of structure (I) has the following structure (IB):


28. The method of claim 16, wherein the compound of structure (I) has the following structure (IB′):


29. The method of claim 16, wherein the compound of structure (I) has the following structure (IC):


30. The method of claim 16, wherein the compound of structure (I) has the following structure (IC′):


31. The method of claim 16, wherein the compound of structure (I) is a pharmaceutically acceptable salt.
 32. The method of claim 31, wherein the pharmaceutically acceptable salt is a base addition salt.
 33. The method of claim 31, wherein the pharmaceutically acceptable salt is a sodium salt.
 34. The method of claim 31, wherein the pharmaceutically acceptable salt is an acid addition salt.
 35. The method of claim 31, wherein the pharmaceutically acceptable salt is a hydrochloride salt.
 36. The method of claim 16, wherein the pharmaceutical composition comprises a pharmaceutically acceptable carrier or excipient and a compound of structure (I).
 37. The method of claim 16, wherein the pharmaceutical composition is formulated for oral delivery. 